As is well known and also disclosed in various prior patent specifications, the high affinity that Ag+ has to --SH and other groups, makes it an efficient biocide for the treatment of water and other liquids. It will be understood that Ag+ ions, in measured doses, are toxic to lower life forms but non-toxic to humans, and in consequence this process can be used to sterilise drinking water. Previous apparatus for these purposes and patent specifications directed thereto have shown however that prior usages have required large and heavy apparatus for Ag+ ion release, as well as complicated apparatus for waterflow control, and also switches at high cost. Such apparatus, electrical circuits and switches have been arranged to release Ag+ ions at a minimal yet reasonably effective rate, but the bulkiness alone would not in the past allow a unit to be made to a size permitting it to be carried manually or in a relatively small suit case or the like.
In the prior art, considerable work has been carried out also in the development and use of apparatus using silver pills for the same purposes, but many problems have been encountered such as having to keep the pills dry, packaging the pills so that the silver does not corrode and so that the Ag+ does not come into contact with the atmosphere prior to use. Since other chemicals may be needed to bind the Ag+ within a pill, such additional chemicals can add further contaminants to the water. Problems also arise in relation to the question of how many pills should be used for a given volume of water.